Perovskite silicon tandem solar cell and method for manufacturing the same

ABSTRACT

Disclosed is a tandem solar cell according to an aspect including: a silicon lower cell; a perovskite upper cell disposed on the silicon lower cell; and a bonding layer for bonding the silicon lower cell and the perovskite upper cell between the silicon lower cell and the perovskite upper cell, wherein the front surface portion of the silicon lower cell being in contact with the bonding layer includes a texture structure, the bonding layer includes a first transparent electrode layer formed on the sidewall of the texture structure, a buried layer filling concave portions of the texture structure on the first transparent electrode layer, and a second transparent electrode layer on top surfaces of the buried layer, the first transparent electrode layer and the texture structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 17/038,740, filed on Sep. 30, 2020, which is based on andclaims priority under 35 U.S.C. § 119 to Korean Patent Application No.10-2019-0121867, filed on Oct. 1, 2019 in the Korean IntellectualProperty Office, and Korean Patent Application No. 10-2020-0112556,filed on Sep. 3, 2020 in the Korean Intellectual Property Office, thedisclosures of which are incorporated by reference herein in theirentireties.

BACKGROUND 1. Field

The present disclosure relates to a tandem solar cell including asilicon lower cell and a perovskite upper cell and a method formanufacturing the same.

2. Description of Related Art

A solar cell is an environmentally-friendly device that converts solarenergy into electric energy. Photovoltaic power generation is enabledwhen sunlight is absorbed into a light absorbing layer of a solar celland electron-hole pairs are generated. Only the incident sunlight havinga bandgap greater than the light absorbing layer is absorbed into thelight absorbing layer, and the energy of the incident sunlight having abandgap not greater than that of the light absorbing layer is consumedas thermal energy. Therefore, in order to efficiently utilize sunlight,tandem solar cells employing a multitude of light absorbing layershaving different bandgaps are receiving much attention.

Perovskite materials currently receiving much attention as lightabsorbing layer materials for next-generation solar cells are capable ofeasily adjusting bandgaps and efficiently distributing incident lightwith respect to a lower cell of the thin film solar cell when the lightabsorbing layer is bonded to the lower cell made of, for example, asilicon, copper indium gallium selenide (CIGS), or copper zinc tinsulfide (CZTS). In addition, the perovskite material is capable offorming a thin film using a low-temperature solution process, and thusthe manufacturing cost may be reduced.

In order to reduce reflection of incident light, the silicon solar cellof the lower cell employs a pyramidal texture structure on its frontsurface portion, and the size of the texture structure is generally inmicrometer (μm) scales. Meanwhile, the perovskite light absorbing layerof the upper cell has a thickness of several hundred nanometers, and itis difficult to uniformly form layers with such a thickness scale on themicrometer-scale texture structure using a solution process.

Therefore, the tandem device including a perovskite upper cell using theconventional solution process and a silicon lower cell having a texturestructure may have a reduced photoelectric conversion efficiency due toa non-uniformly formed perovskite light absorbing layer. Meanwhile, inthe tandem device including a perovskite upper cell using theconventional solution process and a silicon lower cell without a texturestructure, a uniform perovskite layer may be formed in the upper cell,but the loss of light may be unavoidably generated due to the frontsurface reflection of the silicon lower cell.

SUMMARY

In order to solve the problems occurring in the prior art, the presentdisclosure provides a silicon perovskite tandem solar cell capable ofuniformly forming a light conversion layer in a perovskite upper cell ona texture structure of a silicon lower cell using a solution process,and a method for manufacturing the same.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments of the disclosure.

According to an aspect, provided is a tandem solar cell.

The solar cell includes:

a silicon lower cell;

a perovskite upper cell disposed on the silicon lower cell; and

a bonding layer for bonding the silicon lower cell and the perovskiteupper cell between the silicon lower cell and the perovskite upper cell.

The front surface portion of the silicon lower cell being in contactwith the bonding layer may include a texture structure.

The bonding layer may include

a first transparent electrode layer formed on the sidewall of thetexture structure,

a buried layer filling concave portions of the texture structure on thefirst transparent electrode layer, and

a second transparent electrode layer on top surfaces of the buriedlayer, the first transparent electrode layer and the texture structure.

The texture structure may have a truncated pyramid shape.

The second transparent electrode layer may be in contact with the firsttransparent electrode layer exposed between the texture structure andthe buried layer.

The top surfaces of the buried layer, the first transparent electrodelayer and the texture structure may form a flat plane.

The texture structure may have a size in the range of sub micrometers toseveral tens of micrometers.

Each of the first transparent electrode layer and the second transparentelectrode layer may independently include aluminum zinc oxide (AZO),indium tin oxide (ITO), fluorine doped tin oxide (FTO), or indium zincoxide (IZO).

The buried layer may have a lower refractive index than layers adjacentthereto.

The buried layer may include a thermally curable or photocurable polymermaterial.

The buried layer may include an epoxy resin, an acryl resin, a siloxaneresin, a vinyl acetate resin.

The tandem solar cell may further include a lower electrode connected tothe silicon lower cell, and

an upper electrode connected to the perovskite upper cell.

According to another aspect, provided is a method for manufacturing thetandem solar cell.

The method for manufacturing the tandem solar cell may include the stepsof:

forming a pre-texture structure by texturing a front surface portion ofa silicon lower cell;

forming a first transparent electrode layer on the pre-texture structureto a uniform thickness;

forming a buried layer on the first transparent electrode layer to coverthe pre-texture structure;

forming a texture structure by etching top portions of the buried layer,the first transparent electrode layer and the pre-texture structure, andexposing top surfaces of the buried layer filling the concave portionsof the texture structure, the texture structure, and the firsttransparent electrode layer between the buried layer and the texturestructure;

forming a second transparent electrode layer on the exposed top surfacesof the buried layer, the first transparent electrode layer and thetexture structure; and

forming a perovskite upper cell on the second transparent electrodelayer.

The top surfaces of the buried layer, the first transparent electrodelayer and the texture structure may form a flat plane.

The texture structure may have a size in the range of sub micrometers toseveral tens of micrometers.

The step of etching the top portions of the buried layer, the firsttransparent electrode layer and the texture structure may includechemical etching, physical etching or chemical mechanical polishing.

The buried layer may have a lower refractive index than layers adjacentthereto.

The step of forming the perovskite upper cell may include:

forming a hole transport layer on the second transparent electrodelayer;

forming a perovskite light absorbing layer on the hole transport layer;and

forming an electron transport layer on the perovskite light absorbinglayer.

The perovskite light absorbing layer may be formed by a solutionprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional view schematically illustrating aconfiguration of a perovskite silicon tandem solar cell according to anembodiment; and

FIGS. 2A to 2F are schematic cross-sectional views sequentiallyillustrating a method for manufacturing a perovskite silicon tandemsolar cell according to an embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentembodiments may have different forms and should not be construed asbeing limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects of the present description. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items. Expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting of thepresent inventive concept. An expression used in the singularencompasses the expression of the plural, unless it has a clearlydifferent meaning in the context. As used herein, it is to be understoodthat the terms such as “includes,” “have,” and “comprise” are intendedto indicate the presence of the features, numbers, steps, actions,components, parts, ingredients, materials, or combinations thereofdisclosed in the specification, but do not preclude the possibility thatone or more other features, numbers, steps, actions, components, parts,ingredients, materials, or combinations thereof may exist or may beadded.

In the drawings, the diameters, lengths, and thicknesses of layers andregions are exaggerated or reduced for clarity. Throughout thespecification, it is to be understood that when a component, such as alayer, a film, a region, or a plate, is referred to as being “on”another component, the component can be directly on the other componentor intervening components may be present thereon. Throughout thespecification, the terms “first,” “second,” etc. may be used to describevarious elements, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element from another element. In addition, throughoutthe specification and drawings, an identical or corresponding elementwill be referred to as an identical reference numeral, and repeateddescriptions will not be given.

As used herein, a lower cell means a solar cell formed at a lowerportion of a tandem solar cell, and a silicon lower cell means a solarcell in a case where the solar cell formed at the lower portion of thetandem solar cell is a silicon solar cell. Likewise, as used herein, anupper cell means a solar cell formed at an upper portion of a tandemsolar cell, and a perovskite upper cell means a solar cell in a casewhere the solar cell formed at the upper portion of the tandem solarcell is a perovskite solar cell.

As used herein, a texture structure means a structure formed in thesilicon solar cell and may include not only a structure formed by ageneral texturing process but also a structure derived therefrom.

As used herein, a silicon solar cell is a solar cell in which a lightabsorbing layer contains silicon and a perovskite solar cell means asolar cell in which a light absorbing layer contains a material having aperovskite structure.

As used herein, a perovskite light absorbing layer means a lightabsorbing layer including a light absorbing material having a perovskitestructure.

Hereinafter, tandem solar cells according to one or more embodiments anda method for manufacturing the same will be described in further detailwith reference to the accompanying drawings.

<Tandem Solar Cell>

FIG. 1 is a cross-sectional view schematically illustrating aconfiguration of a perovskite silicon tandem solar cell according to anembodiment.

Referring to FIG. 1 , the perovskite silicon tandem solar cell 100includes a silicon lower cell 110, a bonding layer 120 and a perovskiteupper cell 130.

The silicon lower cell 110 may have one of known silicon solar cellstructures, but embodiments of the present disclosure are not limitedthereto. In an example embodiment, the silicon lower cell 110 mayinclude a crystalline silicon substrate (not shown), a p-type amorphousor crystalline silicon layer (not shown), an n-type amorphous orcrystalline silicon layer (not shown), and an amorphous intrinsicsilicon layer (not shown). In addition to the above-described layers,the silicon lower cell 110 may further include additional layers asnecessary.

The front surface portion of the silicon lower cell 110 being in contactwith the bonding layer 120 may have a texture structure 119 having atruncated pyramid shape. The front surface portion of the silicon lowercell 110 may be a silicon layer. The texture structure 119 may have asize in the range of sub micrometers to several tens of micrometers. Inan example embodiment, the texture structure 119 may have a width andheight in the range of 0.1 μm to 5 μm. The texture structure 119 of thesilicon lower cell 110 may reduce the reflection of incident light andincrease the path of the incident light to improve light collectionefficiency, thereby increasing the absorption efficiency of sunlight.

The bonding layer 120 is a layer that physically bonds and electricallyconnects the silicon lower cell 110 and the perovskite upper cell 130 toeach other. The bonding layer 120 includes: a first transparentelectrode layer 121 formed on the sidewall of the texture structure 119of the front surface portion of the silicon lower cell 110; a buriedlayer 123 filling concave portions of the texture structure 119 so as toexpose top surface parts 121 a of the first transparent electrode layer121; and a second transparent electrode layer 125 covering top surfacesof the buried layer 123, the first transparent electrode layer 121 andthe silicon lower cell 110.

The first transparent electrode layer 121 and the buried layer 123 fillthe texture structure 119 of the silicon lower cell 110 to thusplanarize the front surface portion of the silicon lower cell 110. Thesecond transparent electrode layer 125 is formed on the flat top surfaceof the silicon lower cell 110, which is planarized by being filled withthe first transparent electrode layer 121 and the buried layer 123.Since the top surface parts 121 a of the first transparent electrodelayer 121, exposed to the top surface of the silicon lower cell 110, arein contact with the second transparent electrode layer 125, the siliconlower cell 110 is electrically connected to the second transparentelectrode layer 125 through the first transparent electrode layer 121.

Each of the first transparent electrode layer 121 and the secondtransparent electrode layer 125 may independently include a conductivemetal oxide, such as aluminum zinc oxide (AZO), indium tin oxide (ITO),fluorine doped tin oxide (FTO), or indium zinc oxide (IZO). In anexample embodiment, the first transparent electrode layer 121 may have athickness in the range of 5 nm to 300 nm. When the first transparentelectrode layer 121 has a thickness in the range stated above, the firsttransparent electrode layer 121 may be formed on the sidewall of thetexture structure 119 to a uniform thickness, and its surface being incontact with the second transparent electrode layer 125 may be stablymaintained. In an example embodiment, the second transparent electrodelayer 125 may have a thickness in the range of 5 nm to 100 nm. When thefirst transparent electrode layer 121 and the second transparentelectrode layer 125 have a thickness in the range stated above, they maybe electrically connected to each other to serve as a recombinationlayer.

The buried layer 123 may include a transparent material havingrefractive index in the range of about 1 to about 3. The buried layer123 may include, for example, a thermally curable or photocurablepolymer material. The thermally curable or photocurable transparentpolymer material may include, for example, an epoxy resin, an acrylresin, a siloxane resin, a vinyl acetate resin, or a combinationthereof, but embodiments of the present disclosure are not limitedthereto. When the buried layer 123 have the refractive index in therange of about 1 to about 3, the buried layer 123 may have a refractiveindex similar to the layers adjacent thereto. In detail, the buriedlayer 123 may have a similar refractive index to the layers forming thesilicon lower cell 110 and the layers forming the perovskite upper cell130. When the buried layer 123 has a refractive index similar to thelayers adjacent thereto, the reflection of incident light may beminimized. Optionally, the buried layer 123 may further includeconductive particles unless the refractive index or transmission rate isnot affected.

The perovskite upper cell 130 disposed on the bonding layer 120 may haveone of known perovskite solar cell structures, and the structure of theperovskite upper cell 130 is not particularly limited. In an exampleembodiment, the perovskite upper cell 130 may include a hole transportlayer (not shown), a perovskite light absorbing layer (not shown), andan electron transport layer (not shown).

The hole transport layer may include, for example, a conductive polymermaterial or a conductive inorganic material. The conductive polymermaterial may include, for example, polyaniline, polypyrrole,polythiophene, poly-3,4-ethylene dioxythiophene-polystyrene sulfonate(PEDOT-PSS), poly-[bis(4-phenyl)(2,4,6-trimethylphenyl)amine](PTAA),spiro-MeOTAD or polyaniline-camphor sulfonic acid (PANI-CSA), butembodiments of the present disclosure are not limited thereto. Theconductive inorganic material may include NiO, WO₃, or CuSCN, butembodiments of the present disclosure are not limited thereto. In anexample embodiment, the hole transport layer may have a thickness in therange of 5 nm to 300 nm.

The light absorbing layer may include a light absorbing material havinga perovskite structure. The light absorbing layer having a perovskitestructure may include, for example, organic halide perovskite or metalhalide perovskite.

The organic halide perovskite may include, for example, CH₃NH₃Pbl₃,CH₃NH₃Pbl_(x)Cl_(3-x), CH₃NH₃Pbl_(x)Br_(3-x), CH₃NH₃PbCl_(x)Br_(3-x),HC(NH₂)₂Pbl₃, HC(NH₂)₂Pbl_(x)Cl_(3-x), HC(NH₂)₂Pbl_(x)Br_(3-x),HC(NH₂)₂PbCl_(x)Br_(3-x), (CH₃NH₃)(HC(NH₂)₂)_(1-y)Pbl₃,(CH₃NH₃)(HC(NH₂)₂)_(1-y)Pbl_(x)Cl_(3-x),(CH₃NH₃)(HC(NH₂)₂)_(1-y)Pbl_(x)Br_(3-x), or(CH₃NH₃)(HC(NH₂)₂)_(1-y)PbCl_(x)Br_(3-x) (0≤x≤1, 0≤y≤1), but embodimentsof the present disclosure are not limited thereto. In addition, acompound partially doped with Cs or Rb in the organic ammonium moietymay also be used as the organic halide perovskite. The metal halideperovskite may include, for example, lead iodide (Pbl2), lead bromide(PbBr) or lead chloride (PbCl2). The light absorbing layer may have athickness in the range of several tens to several hundreds ofnanometers. In an example embodiment, the light absorbing layer may havea thickness in the range of 100 nm to 1000 nm.

The electron transport layer may include, for example, TiO₂, SnO₂, ZnO,TiSrO₃, graphene, carbon nanotubes, [6,6]-phenyl-C₆₁-butyric acid methylester (PCBM), or a combination thereof, but embodiments of the presentdisclosure are not limited thereto. In an example embodiment, theelectron transport layer may have a thickness in the range of 1 nm to300 nm.

In addition to the above-described layers, the perovskite upper cell 130may further include additional layers as necessary.

In addition, the perovskite silicon tandem solar cell 100 may furtherinclude a lower electrode (not shown) connected to the silicon lowercell 110 and an upper electrode (not shown) connected to the perovskiteupper cell 130.

The perovskite silicon tandem solar cell according to the presentembodiment may have an increased absorption efficiency of the sunlightby reducing the reflection of the sunlight using the texture structureof the silicon lower cell. In addition, a bonding layer is planarlyformed on the texture structure, thereby forming the perovskite uppercell reliably.

<Manufacturing Method of Tandem Solar Cell>

FIGS. 2A to 2E are schematic cross-sectional views sequentiallyillustrating a method for manufacturing a perovskite silicon tandemsolar cell according to an embodiment.

First, referring to FIG. 2A, a pre-texture structure 118 may be formedby texturing a front surface portion of a silicon lower cell 110. Thefront surface portion of the silicon lower cell 110 may be a siliconlayer. Although not shown in FIG. 2A, as described above, the siliconlower cell 110 may include a p-type amorphous or crystalline siliconlayer (not shown), an n-type amorphous or crystalline silicon layer (notshown), and an amorphous intrinsic silicon layer (not shown), and mayhave a variety of structures without being limited thereto. Thetexturing may be performed through, for example, etching or grooving.The pre-texture structure 118 may have, for example, a pyramidal shape.At the time of etching for texturing, for example, a basic solution,such as potassium hydroxide (KOH) or sodium hydroxide (NaOH), or an acidsolution, such as nitric acid (HNO3) or fluoric acid (HF). The groovingfor texturing may be performed using, for example, laser. Meanwhile, arear surface portion of the silicon lower cell 110 may have a texturestructure or a planar structure.

Referring to FIG. 2B, a first transparent electrode layer 121 may beformed on the pre-texture structure 118. The first transparent electrodelayer 121 may be made of a conductive metal oxide, such as, for example,ITO, AZO, FTO, or IZO. The conductive metal oxide of the firsttransparent electrode layer 121 may be formed using, for example,sputtering or spin coating. In an example, the first transparentelectrode layer 121 may be conformally formed to have a uniformthickness so as to maintain irregularities of the texture structure 119.In an example embodiment, the first transparent electrode layer 121 mayhave a thickness in the range of 5 nm to 300 nm.

Referring to FIG. 2C, a buried layer 123 may be formed on the firsttransparent electrode layer 121 so as to cover completely thepre-texture structure 118 of the silicon lower cell 110. The buriedlayer 123 may be made of, for example, a thermally curable orphotocurable polymer material having a refractive index in the range ofabout 1 to about 3. The buried layer 123 may be made of, for example, anepoxy resin, an acryl resin, a siloxane resin, a vinyl acetate resin, ora combination thereof. Optionally, the buried layer 123 may furtherinclude conductive particles. The buried layer 123 may be formed to havean appropriate thickness so as to perform a planarization process on thelower texture structure 119.

Referring to FIG. 2D, the top surface of the silicon lower cell 110 maybe planarized while exposing the first transparent electrode layer 121,by etching top portions of the buried layer 123, the first transparentelectrode layer 121 and the pre-texture structure 118. During theplanarization process, chemical etching, physical etching or chemicalmechanical polishing may be used. In an example embodiment, a compoundor a suspension, including silica, diamond, alumina or cesium oxide, maybe used to perform the chemical mechanical polishing. The top portion ofthe pre-texture structure 118 is etched to form a texture structure 119,and the top surface of the buried layer 123 filling the concave portionsof the texture structure 119 and top surface parts 121 a of the firsttransparent electrode layer 121 are exposed.

Referring to FIG. 2E, a second transparent electrode layer 125 may beformed on the texture structure 119, the first transparent electrodelayer 121 and the buried layer 123, which are exposed after the etchingfor planarization. The second transparent electrode layer 125 mayinclude, for example, AZO, ITO, FTO, or IZO. The second transparentelectrode layer 125 may be made of the same material as the firsttransparent electrode layer 121. Optionally, the second transparentelectrode layer 125 may be made of a different material from the firsttransparent electrode layer 121. The second transparent electrode layer125 is in contact with the first transparent electrode layer 121 to thenbe electrically connected thereto. The first transparent electrode layer121, the buried layer 123 and the second transparent electrode layer 125may form a bonding layer 120 connecting the silicon lower cell 110 andthe perovskite upper cell 130. Electrons from the silicon lower cell 110and holes from the perovskite upper cell 130 are recombined at the firsttransparent electrode layer 121 and the second transparent electrodelayer 125 in the bonding layer 120, thereby maintaining chargeneutrality.

Referring to FIG. 2F, the perovskite upper cell 130 may be formed on thesecond transparent electrode layer 125. The perovskite upper cell 130may be formed by a publicly known method. Although not shown in FIG. 2F,the perovskite upper cell 130 may include a hole transport layer, alight absorbing layer, and an electron transport layer. As to the holetransport layer, the light absorbing layer and the electron transportlayer according to the present embodiment, reference may be made to thedescription of the tandem solar cell according to the previousembodiment.

In an example embodiment, the hole transport layer, the light absorbinglayer and the electron transport layer may be sequentially formed on thesecond transparent electrode layer 125, thereby forming the perovskiteupper cell 130. The hole transport layer may be formed by, for example,spin coating or thermally evaporating a conductive polymer or aconductive inorganic material such as NiO, WO₃ or CuSCN on secondtransparent electrode layer 125. The light absorbing layer may be formedon the hole transport layer using a light absorbing material having aperovskite structure. The light absorbing layer may be formed by, forexample, spin coating a solution prepared by dissolving a precursormaterial of organic halide perovskite or metal halide perovskite on thehole transport layer. The electron transport layer may be formed on thelight absorbing layer using, for example, TiO₂, SnO₂, ZnO, TiSrO₃,graphene, carbon nanotubes or PCBM, by sol-gel method, spin coating orthermal evaporation. In another example embodiment, the electrontransport layer may be formed on the second transparent electrode layer125, and the hole transport layer may be formed on the the lightabsorbing layer. According to another embodiment, additional layers maybe further formed when forming the perovskite upper cell 130.

According to embodiments of the present disclosure, the top portion ofthe texture structure formed on the front surface portion of the siliconlower cell may be planarized at the time of forming a bonding layer, andthus a perovskite upper cell may be easily and reliably formed at lowcost by employing a solution process. The thus formed perovskite silicontandem solar cell may have an increased photoelectric conversionefficiency by forming the perovskite upper cell reliably whilemaintaining the texture structure of the silicon lower cell.

According to the configuration of the perovskite silicon tandem solarcell and the method for manufacturing the same of the presentdisclosure, a perovskite upper cell may be reliably formed on a siliconlower cell having a texture structure on the front surface portionthereof using a solution process, and thus the perovskite silicon tandemsolar cell having excellent performance may be manufactured.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments. While one or more embodiments have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope of thedisclosure as defined by the following claims.

What is claimed is:
 1. A method for manufacturing a tandem solar cell,the method comprising the steps of: forming a pre-texture structure bytexturing a front surface portion of a silicon lower cell; forming afirst transparent electrode layer on the pre-texture structure to auniform thickness; forming a buried layer on the first transparentelectrode layer to cover the pre-texture structure; forming a texturestructure by etching top portions of the buried layer, the firsttransparent electrode layer and the pre-texture structure, and exposingtop surfaces of the buried layer filling the concave portions of thetexture structure, the texture structure, and the first transparentelectrode layer between the buried layer and the texture structure;forming a second transparent electrode layer on the exposed top surfacesof the buried layer, the first transparent electrode layer and thetexture structure; and forming a perovskite upper cell on the secondtransparent electrode layer.
 2. The method of claim 1, wherein the topsurfaces of the buried layer, the first transparent electrode layer andthe texture structure forms a flat plane.
 3. The method of claim 1,wherein the texture structure has a size in the range of sub micrometersto several tens of micrometers.
 4. The method of claim 1, wherein thestep of etching the top portions of the buried layer, the firsttransparent electrode layer and the texture structure comprises chemicaletching, physical etching or chemical mechanical polishing.
 5. Themethod of claim 1, wherein the buried layer comprises a thermallycurable or photocurable polymer material.
 6. The method of claim 1,wherein the step of forming the perovskite upper cell comprises: forminga hole transport layer on the second transparent electrode layer;forming a perovskite light absorbing layer on the hole transport layer;and forming an electron transport layer on the perovskite lightabsorbing layer.
 7. The method of claim 1, wherein the perovskite lightabsorbing layer is formed by a solution process.